Wikipedia:
"Computer programming is the process of building and designing an executable computer program for accomplishing a specific computing task"
Endless possibilities!
| Old versions | Python 3 |
|---|---|
| Python 1.0 - January 1994 | Python 3.0 - December 3, 2008 |
| Python 1.0 - January 1994 | Python 3.1 - June 27, 2009 |
| Python 1.2 - April 10, 1995 | Python 3.2 - February 20, 2011 |
| Python 1.3 - October 12, 1995 | Python 3.3 - September 29, 2012 |
| Python 1.4 - October 25, 1996 | Python 3.4 - March 16, 2014 |
| Python 1.5 - December 31, 1997 | Python 3.5 - September 13, 2015 |
| Python 1.6 - September 5, 2000 | Python 3.6 - December 23, 2016 |
| Python 2.0 - October 16, 2000 | Python 3.7 - June 27, 2018 |
| Python 2.1 - April 17, 2001 | Python 3.8 - October 14, 2019 |
| Python 2.2 - December 21, 2001 | Python 3.9 - October 5, 2020 |
| Python 2.3 - July 29, 2003 | Python 3.10 - October 4, 2021 |
| Python 2.4 - November 30, 2004 | |
| Python 2.5 - September 19, 2006 | |
| Python 2.6 - October 1, 2008 | |
| Python 2.7 - July 3, 2010 |
After this course you should be able to:
How to seek help:
# A simple loop that adds 2 to a number
i = 0
while i < 10:
u = i + 2
print('u is' + str(u))
i += 1
u is2 u is3 u is4 u is5 u is6 u is7 u is8 u is9 u is10 u is11
'this is a string'
"this is also a string"
3 # here we can put a comment so we know that this is an integer
3.14 # this is a float
True # this is a boolean
type(True)
bool
[3, 5, 7, 4, 99] # this is a list of integers
('a', 'b', 'c', 'd') # this is a tuple of strings
{'a', 'b', 'c'} # this is a set of strings
{'a':3, 'b':5, 'c':7} # this is a dictionary with strings as keys and integers as values
type([3, 5, 7, 4, 99])
list
That depends on their type:
'a string'+' another string'
2 + 3.4
'a string ' * 3
#'a string ' * 3.4
'a string a string a string '
Type Operations
int + - / ** % // ...
float + - / * % // ...
string +
Used to store values and to assign them a name.
Examples:
i = 0counter = 5snpname = 'rs2315487'snplist = ['rs21354', 'rs214569'] width = 23564
height = 20
snpname = 'rs56483 '
snplist = ['rs12345','rs458782']
snpname * 3
'rs56483 rs56483 rs56483 '
Allowed: Not allowed:
Var_name 2save
_total *important
aReallyLongName Special%
with_digit_2 With spaces
dkfsjdsklut (well, allowed, but NOT recommended)
NO special characters:
+ - * $ % ; : , ? ! { } ( ) < > “ ‘ | \ / @
→ Notebook Day_1_Exercise_1 (~30 minutes)
width = 5
height = 3.6
snps = ['rs123', 'rs5487']
snp = 'rs2546'
active = True
nums = [2,4,6,8,4,5,2]
#sum(width)
x = 4
y = 3
z = [2, 3, 6, 3, 9, 23]
pow(x, y)
64
x = 5
y = 3
y == x
False
x = 2
y = 3
x == 2 or y == 5
x = [2,4,7,3,5,9]
y = ['a','b','c']
2 in x
4 in x and 'd' in y
False
# A simple loop that adds 2 to a number and checks if the number is even
i = 0
even = [2,4,6,8,10]
while i < 10:
u = i + 2
print('u is '+str(u)+'. Is this number even? '+str(u in even))
i += 1
u is 2. Is this number even? True u is 3. Is this number even? False u is 4. Is this number even? True u is 5. Is this number even? False u is 6. Is this number even? True u is 7. Is this number even? False u is 8. Is this number even? True u is 9. Is this number even? False u is 10. Is this number even? True u is 11. Is this number even? False
# A simple loop that adds 2 to a number, check if number is even and below 5
i = 0
even = [2,4,6,8,10]
while i < 10:
u = i + 2
print('u is '+str(u)+'. Is this number even and below 5? '+\
str(u in even and u < 5))
i += 1
u is 2. Is this number even and below 5? True u is 3. Is this number even and below 5? False u is 4. Is this number even and below 5? True u is 5. Is this number even and below 5? False u is 6. Is this number even and below 5? False u is 7. Is this number even and below 5? False u is 8. Is this number even and below 5? False u is 9. Is this number even and below 5? False u is 10. Is this number even and below 5? False u is 11. Is this number even and below 5? False
x = 5
y = 7
z = 2
x == 5 and y < 7 or z > 1
# and binds stronger than or
x > 4 or y == 6 and z > 3
x > 4 or (y == 6 and z > 3)
(x > 4 or y == 6) and z > 3
False
# BEWARE!
x = 5
y = 8
#xx == 6 or xxx == 6 or x > 2
x > 42 or (y < 7 and xx > 1000)
False
Python does short-circuit evaluation of operators
Lists (and strings) are an ORDERED collection of elements where every element can be accessed through an index.
l = [2,3,4,5,3,7,5,9]
s = 'some longrandomstring'
'o' in s
l[2]
s[0:7]
s[0:8:2]
s[-1]
l[0] = 42
#s[0] = 'S'
Mutable objects can be altered after creation, while immutable objects can't.
Immutable objects: Mutable objects:
int • listfloat • setbool • dictstrtuples = [0,1,2,3,4,5,6,7,8,9]
s.insert(5,10)
#s.reverse()
s.append(10)
s
[0, 1, 2, 3, 4, 10, 5, 6, 7, 8, 9, 10]
→ Notebook Day_1_Exercise_2 (~30 minutes)
fruits = ['apple','pear','banana','orange', 'grapes']
print(fruits[0])
print(fruits[1])
print(fruits[2])
print(fruits[3])
print(fruits[4])
apple pear banana orange grapes
fruits = ['apple','pear','banana','orange', 'grapes']
for fruit in fruits:
print(fruit)
print('hello')
print('done')
apple pear banana orange grapes hello done
Always remember to INDENT your loops!
For loop¶fruits = ['apple','pear','banana','orange']
mystring = 'mylongstring'
for fruit in fruits:
print(fruit)
apple pear banana orange
While loop¶fruits = ['apple','pear','banana','orange']
i = 0
while i < len(fruits):
print(fruits[i])
i = i + 1
print(i)
apple pear banana orange 4
For loop
Is a control flow statement that performs a fixed operation over a known amount of steps.
While loop
Is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition.
Which one to use?
For loops better for simple iterations over lists and other iterable objects
While loops are more flexible and can iterate an unspecified number of times
→ Notebook Day_1_Exercise_3 (~20 minutes)
if/else statementsshopping_list = ['bread', 'egg', 'butter', 'milk']
if len(shopping_list) > 3:
print('Go shopping!')
else:
print('Nah! I\'ll do it tomorrow!')
Go shopping!
shopping_list = ['bread', 'egg', 'butter', 'milk']
tired = True
if len(shopping_list) > 3:
if not tired:
print('Go shopping!')
else:
print('Too tired, I\'ll do it later')
else:
if not tired:
print('Better get it over with today anyway')
else:
print('Nah! I\'ll do it tomorrow!')
Too tired, I'll do it later
Any longer pieces of code that have been used and will be re-used SHOULD be saved
Two options:
./script.pypython script.pyfruits = ['apple','pear','banana','orange']
for fruit in fruits:
print(fruit)
apple pear banana orange
fh = open('../files/fruits.txt', 'r', encoding = 'utf-8')
for line in fh:
print(line)
fh.close()
apple pear banana orange
'string'.strip() Removes whitespace
'string'.split() Splits on whitespace into list
s = ' an example string to split with whitespace in end '
sw = s.strip()
sw
l = s.split()
#l = s.strip().split()
l
['an', 'example', 'string', 'to', 'split', 'with', 'whitespace', 'in', 'end']
xx = open('../files/fruits.txt', 'r', encoding = 'utf-8')
for line in xx:
print(line.strip())
fh.close()
apple pear banana orange
How much money is spent on ICA?
fh = open("../files/bank_statement.txt", "r", encoding = "utf-8")
total = 0
times = 0
for line in fh:
expenses = line.strip().split() # split line into list
store = expenses[0] # save what store
price = float(expenses[1]) # save the price
if store == 'ICA': # only count the price if store is ICA
times = times + 1
total = total + price
fh.close()
print('Total amount spent on ICA is: '+str(total))
print(times)
Total amount spent on ICA is: 1186.71 3
How much money is spent on ICA in September?
fh = open("../files/bank_statement_extended.txt", "r", encoding = "utf-8")
total = 0
for line in fh:
if not line.startswith('store'):
expenses = line.strip().split()
store = expenses[0]
year = expenses[1]
month = expenses[2]
day = expenses[3]
price = float(expenses[4])
if store == 'ICA' and month == '09': # store has to be ICA and month september
total = total + price
fh.close()
out = open("../files/bank_statement_results.txt", "w", encoding = "utf-8") # open a file for writing the results to
out.write('Total amount spent on ICA in september is: '+str(total))
out.close()
for file in os.scandir("../files/"):
print(time.ctime(os.stat(file).st_mtime), '\t', file.name)
Thu May 20 17:46:00 2021 bank_statement.txt Thu May 20 17:46:00 2021 bank_statement_extended.txt Thu Sep 8 16:31:04 2022 bank_statement_results.txt Thu May 20 17:46:00 2021 blocket_listings_selected.txt Thu May 20 17:46:01 2021 cheat_sheet.pdf Thu May 20 17:46:01 2021 fruits.txt Thu May 20 17:46:01 2021 fruits_extended.txt Thu Oct 21 12:53:44 2021 schedule.csv Thu May 20 17:46:01 2021 somerandomfile.txt
For loops and While loopsIf/Else statement are used when deciding actions depending on a condition that evaluates to a booleanIf/Else statements can be nestedopen() can be used to read in text files→ Notebook Day_1_Exercise_4